1. Field of Invention
The present invention relates to an apparatus for feeding or loading fine particulate material into industrial plant equipment and to a portable dust collector for filtering and removing of dust and particulate materials that are generated in industrial plants, such as foundry furnaces. The present invention more particularly relates to an apparatus for feeding and loading fine particulate material, such as fine silica powder, into foundry furnaces and to a portable dust collector for removing such dust and fine particulate materials during relining operations of foundry furnaces.
2. Description of the Related Art
Generation of dust and fine particulate materials, e.g., fine silica powder, in industrial plants is a particular vexing and serious health problem. The U.S. Department of Labor's Occupational Safety and Health Administration (OSHA) has established regulations that set forth safety guidelines and industrial standards that are required to be met owners in the operation of industrial plants for the protection of employee's health and safety. For example, OSHA has established guidelines in the U.S. metal-casting industry, which includes foundry furnace industry, for exposure to silica in the workplace and includes a maximum exposure limit of 20 parts per million (ppm) for crystalline silica in an 8-hour day.
Recently, attesting to the significance of silica as a workforce safety hazard, the America Foundry Society (AFS) and OSHA the signed a two year new alliance agreement to continue joint efforts to promote safer and more healthful workplaces in the U.S. metal-casting industry that will help AFS members protect employee's health and safety, particularly focusing on workplace issues, including personal protective equipment, ventilation and reducing and preventing exposure to silica.
Exposure to silica particulates is especially seen as hazardous in the foundry industry, such as the coreless induction furnaces, which require frequent installing of the refractory (e.g., silica) liners. Heretofore, the fine silica powder was delivered in bags, which were then opened by workers by slitting the bag and dumping the fine silica powder into the annulus formed by a sacrificial metal liner (furnace form) and the furnace exterior wall. This technique is quite dirty and generates large amounts of very fine silica powder and dust particulates that float around in the air and may create health problems for the workers. Typically, foundry furnace operators pull a vacuum over the furnace freeboard above the open reactor vessel to reduce the level of silica powder and dust particulates exposure to their workers. Workers also typically wear personal protective equipment, including respirators, masks, etc., to attempt to filter out the fine silica powder and dust particulates but the silica powder and dust particulates are so pervasive that they continue to present health hazards due to ingestion of fine silica powder and dust particulates, which can lead to silicosis an incurable lung disease.
Other more conventional feed devices include one, for example, described in U.S. Pat. No. 2003/0015812 A1, which involves a method for installing a refractory lining in coreless or channel electric induction furnaces by adding dry refractory material between a liner form and an inner wall of the furnace. There, a simple funnel is used for placement of the refractory material in a coreless electric furnace. While the use of a funnel is possibly beneficial in better directing the dry refractory material into the annulus formed by the liner form and the inner wall of the furnace, it obviously generates dust and fine particulate material into the atmosphere surrounding the furnace, which creates a hazardous condition for the foundry workers installing the refractory liners.
Another feed apparatus for loading particulate material into foundry furnaces, such as cylindrical coreless electric furnaces, is described in U.S. Pat. No. 5,058,776. This patent discloses an apparatus for dispensing particulate material for foundry furnaces into an annulus formed by the furnace wall and an expendable cylindrical form. In particular there is provided a cylindrical platform covering the top of the expendable metal form and adapted to rotate around the center line axis of the metal form by a carriage rotatably mounted on the platform and riding on wheels that travel along a circular track that is inboard and concentric with the annulus formed between the furnace wall and the metal expendable form. The cylindrical platform includes a circular rim that fits about the open top of the expendable liner to position the apparatus. A hopper is carried on the top of the cylindrical platform having an opening in the lower end for discharging the particulate material into the annulus. A motor is also provided for rotating the cylindrical platform around the top of the cylindrical metal form. While this apparatus provides a delivery system for particulate material into foundry furnaces, such as coreless electric furnaces, it is expensive and complex to operate.
As noted above, these prior art feed apparatuses and designs provide little or no protection for workers who are dispensing the particulate material in foundry furnaces, such as a coreless electric furnace. Viewing U.S. Pat. No. 5,058,776, above, there is noted that the feed dispensing apparatus disclosed therein is open to the atmosphere and any particulate dust would be carried into the atmosphere that surrounds the operator and like conventional prior art apparatuses, e.g., funnels, provide no reduction of the particulate dust formed in the furnace re-lining operation. Thus, while these prior art devices address apparatuses for the introduction of particulate material into foundry furnaces during the re-lining operation, they offer little or no abatement of the generated dust or fine particulate material, such as fine silica powder, during the critical furnace re-lining operation which depending on the size and through-put (as measured in tons) of metal must be repeated every 2-4 weeks.
Thus, it may be seen that there is a need to provide a simple, less costly feed apparatus for use in delivering particulate materials, such as fine silica powders, into foundry furnaces, e.g., coreless electric furnaces. There also is a need to provide a cost effective and efficient dust collector for use in removing fine dust and particulate materials (e.g., fine silica powders) in foundry operations, such as in re-lining operations of coreless electric furnaces.